Disposable cassette systems are widely used, particularly in medical applications involving the handling of fluids that interact with biological systems. Examples are to be found in U.S. Pat. Nos. 4,493,695, 4,627,833, and 4,713,051.
Where blood is the fluid being transferred, the dangers of contamination are high, and consequently it is generally preferred to utilize disposable tubing and fluid transfer systems rather than attempt to sterilize part or all of the fluid handling system for each use. Incorporation of the essential elements in a relatively low cost cassette minimizes removal and handling time and the dangers of an incorrect setup. The same is true in fluid interchange systems used for ophthalmic surgical applications, such as irrigation and aspiration systems of the type sold by Site, a Johnson & Johnson subsidiary, under their Model No. TXR, and by CooperVision, now Alcon, under the Model 10,000. The Model 10,000 is essentially described in U.S. Pat. No. 1,713,051 to Steppe, et al. and represents a cassette adaptation of an earlier Model 8000 that employed loose tubing sets with peristaltic pumps and passed waste matter to a plastic bag. The Site cassette, as evidenced by U.S. Pat. No. 4,627,833 to Cook, disposes irrigation and aspiration lines in a rectangular package having an attached rigid collection vessel. Within the cassette body, there are complex flexible tubing paths. In both systems internal flexible lines are juxtaposed so that clamp actuators in the console may pinch exposed lines against internal surfaces to stop flow, after the cassette is inserted. In operation of both systems, sterile irrigation fluid from a source is fed by gravity to the operative site, and aspirated therefrom back to a collection unit.
In the Site device, the aspiration line is coupled to a reciprocating diaphragm pump, whereas in the CooperVision system, the coupling is to a peristaltic pump. The Coopervision cassette is configured in a conventional fashion to have a semicircular boss against which the rollers of the peristaltic pump may press the irrigation line so as to establish the needed transfer force on the irrigation fluid. The Site unit couples the aspiration line into a rigid container attached directly to the cassette, within which a lowered pressure is created by a suction line from the pump.
In parent application, U.S. patent Ser. No. 07/324,018, now U.S. Pat. No. 4,963,131 to the instant application, it is shown that the use of internal sliders within a cassette body to transfer force from an external clamp actuator internally into a selected location or locations within the cassette has a number of particular advantages. By confining the area of repeated flexure of the transfer lines to well within the body of the cassette, the danger of contamination of sterile flows upon the occurrence of cracks or pinholes in the line due to repeated flexure is greatly minimized. Also, the line geometries within the cassette are straightened, shortened and simplified by virtue of the degrees of design freedom that are available. Thus a number of operative and mechanical advantages are obtained at no substantial increase in cost.
The cost of disposable cassettes is, however, an item of constant concern as health care expenses continue to mount. A dramatic decrease in the cost of disposable units, without sacrifice of sterility or operative advantages is greatly to be desired.